A Belgian White beer can be either an ale or a lager, but are always wheat beers or weizen biers and almost certainly include some sort of spices in the brewing process. The most common spices found in a white beer is coriander and lemon zest.
These are crisp, light and refreshing beers that are perfect for the summer time. A good example of an American style white beers is Lost Coast Great White.
A few more examples:
Hoegaarden: from Belgium, this beer is fruiter than some with notable orange flavors.
Blanche de Chamblis: a spicy beer with more pronounced coriander flavor from an area outside Montreal.
Whirlwind Wit Beer: from Victory Brewing in Pennsylvania.
Sunshine Wheat Beer: from New Belgium Brewing Co. in Fort Collins, Colorado.
Other informative beer resources...
Wheat - Wheat beers have become very popular in recent years, and are especially popular in warm weather. Find out more about this beer style.